1. Field of the Invention
The present invention relates to a fluid-tight closure apparatus and, more particularly, to an apparatus for providing a fluid-tight seal between the inner surface of a cylindrical bore in an enclosure receiving a high-pressure fluid, such as the casing of a turbo machine or other cylindrical pressure vessel, and the outer peripheral surface of an end closure wall which is held in the cylindrical bore.
2. Description of the Prior Art
In enclosures having a high internal pressure, particularly casings of turbo machines handling high-pressure fluids, a closure apparatus is used in which an end closure wall for closing the opening end of the casing can be easily attached to and detached from the casing. The closure apparatus for this purpose is usually provided with a fixing or stop member, for example, such as shearing key by means of which the end closure wall is fixed in the end opening of the cylindrical bore in the enclosure, against the axial movement of the end closure wall which might, for otherwise, be caused by the internal pressure in the enclosure.
This type of closure apparatus is disclosed, for example, in British Pat. No. 1,396,457 and U.S. Pat. No. 3,874,814. In these closure apparatus, the outer peripheral surface of the end closure wall and the inner peripheral surface of the cylindrical bore in the enclosure in combination constitute the sealing surfaces against the leakage of the fluid. Usually, "O" rings or the like elastic sealing members are used as the sealing means interposed between the sealing surfaces. These sealing members such as "O" rings are, however, not durable enough especially when the temperature and the pressure of the fluid in the enclosure are high.
Under this circumstance, it has been proposed and attempted to use sealing means including a metallic gasket packing. In this sealing means, the outer peripheral surface of the end closure wall is partially tapered so that the metallic gasket packing interposed between the tapered surface of the end closure wall and the inner peripheral surface of the cylindrical bore may be expanded radially outwardly into tight contact with the latter, by the axial displacement of the end closure wall due to the internal fluid pressure.
This sealing means including the metallic gasket packing, is capable of improving the sealing performance, on the other hand poses a new problem that a large stress exceeding the yielding point is caused in the metallic gasket packing, due to the radial force imparted to the latter by the tapered surface of the end closure wall due to the pressure in the enclosure. Once the metallic gasket packing is collapsed, it can no longer be used, and a troublesome disassembling work is required for the removal of the collapsed packing.